Standardised Candle Method For SNII

Many Type II light curves display a prominent plateau phase where the brightness of the supernova remains roughly constant over an extended period of time. Astronomers have found that the luminosity of this plateau is correlated with the energy of the explosion and the expansion velocities of the ejected material. This means that the luminosities of the plateau supernovae (SNII-P) can be standardised from a spectroscopic measurement of the ejecta velocity. This is known as the Standardised Candle Method for Type II supernovae, and provides an opportunity to determine distances to these objects independent from those calculated via the Expanding Photosphere Method (EPM).

While the standardised method for SNII distances does rely on the calibration of the cepheid variable distance scale (EPM is independent of this calibration), the distances determined for the SNII are accurate to about 9%. This is better than what can be achieved via EPM (~20%), and approaches the accuracy of the currently favoured distance indicator – Type Ia supernovae.